Reactive streams and components on OSGi

Transcript

1. Reactive streams and components on OSGi Christian Schneider
2. Christian Schneider » For the last 6 years: Open Source Architect at Talend » Since October: Computer scientist at Adobe. » Apache member and committer » Twitter @schneider_chris » Website liquid-reality.de
3. Reactive … sounds good ... but what is it really? Responsive Resilient Elastic Message Driven Source: http://www.reactivemanifesto.org/
4. Reactive Streams Spec http://www.reactive-streams.org/ Publisher Subscriber Processor Subscription Extends both creates uses
5. Reactive Streams implementations Reactor
6. Backpressure Subscriber Subscription Publisher subscribe onsubscribe publisher.subscribe(subscriber) subscriber.onSubscribe(subscription) subscription.request(num events) subscriber.onNext(T event) onComplete() pull Async push limited to requested num
7. Pull based approach Good for pull based protocols • JMS • Kafka • Imap Not so good for push based protocols • HTTP • EventAdmin • MQTT
8. ProjectReactor.io » Built on reactive streams api » Core of Spring 5 » Very similar to rxjava but optimized for Java 8+ » No additional dependencies » OSGi ready Flux.interval(of(1, ChronoUnit.MILLIS)) .window(2, 1) .flatMap(win -> MathFlux.averageDouble(win)); .subscribe(System.out::println); 0.5, 1.5, 2.5, 3.5, ...
9. Apache Karaf Reactive components » Component API » No built in DSL » Use any DSL based on reactive streams API » Optimized for OSGi but also works in plain java public interface RComponent { <T> Publisher<T> from(String destination, Class<T> type); <T> CloseableSubscriber<T> to(String destination, Class<T> type); }
10. Mqtt Reactive Component Configuration Mqtt component Service RComp name=mqtt
11. Using reactive components Retrieve the mqtt reactive component as a service @Reference(target="(name=mqtt)") RComponent mqtt; Send a counter to mqtt every second Flux.interval(Duration.ofSeconds(1)) .map(ByteArrayConverter::fromLong) .subscribe(mqtt.to("input", byte[].class));
12. Why not Apache Camel? » No separate component API. All components depend on camel core » Acquired too many features over time without proper design changes (async, transactions, tracing, …) » No support for backpressure
13. Reactive Components and Camel » Bridging from reactive components to camel is possible => using camel-rx Adapter » Camel component for reactive components http://camel.apache.org/rx.html
14. Why not OSGi push streams instead of reactive streams? » OSGi Push streams is a great DSL and engine but » Only used on OSGi -> much smaller eco system » Not compatible to reactive streams API » Does not have a small API suitable for components » Can not be used with a different DSL
15. Demo time Reactive in action
16. Reactive Is it the golden hammer? » Can make system a lot more resilient in high load situations (backpressure) » Makes it easier to code in an asynchronous way but » Only works well if all steps are non blocking » Much of the infrastructure as well as user code is still blocking » Coding in a reactive DSL is a very steep learning curve
17. Thanks for your attention Questions?
18. Further reading Project Reactor Reactive Components Reactive Streams Push stream examples